This invention relates to a structure of fixing a one-way clutch to a housing. The invention can also be applied to a so-called rolling bearing-integrated one-way clutch in which a one-way clutch and a rolling bearing have common outer or inner rings.
Generally, a one-way clutch includes a plurality of wedge elements (such as sprags or rollers), and an urging member for urging these wedge elements in a predetermined direction (locking direction). Sprags, rollers or the like are used as the wedge elements, and when the inner and outer rings rotate relative to each other, a torque is transmitted in one direction only by the interaction between the shape of the wedge elements and the shape of a space between the inner and outer rings, and the inner and outer rings idle relative to each other in the other direction. There is also known a so-called rolling bearing-integrated one-way clutch in which the outer ring and inner ring of such a one-way clutch serve also as common at least one of outer and inner rings for a rolling bearing.
In the above one-way clutch, usually, the inner ring is fixed to a shaft, while the outer ring is received within a housing, and is fixed thereto so that the torque transmission/idling is effected between the shaft and the housing. Therefore, the inner ring and the shaftd need to move in unison, while the outer ring and the housing need to move in unison. Therefore, the inner ring and the shaft are fittingly fixed to each other by interference fit, while the outer ring and the housing are fittingly fixed to each other by interference fit.
Incidentally, in the case where the housing is formed, for example, by press working, and its dimensional accuracy and shape accuracy are low, it is difficult to control the dimension of the outer diameter of the outer ring so as to fit the outer ring in the housing by the predetermined interference fit. As a technique for solving this problem, there has been proposed a one-way clutch (see, for example, Patent Literature 1) in which an eccentric groove is formed in an outer periphery of an outer ring, and a stop ring with an outwardly-projecting pressing portion, is mounted in the eccentric groove so that a so-called creep phenomenon (in which the outer ring and a housing rotate relative to each other) will not occur even when a certain degree of clearance exists between the outer ring and the housing.
Patent Literature 1: JP-A-11-108084
In the above related creep prevention technique in which the stop ring is mounted in the eccentric groove formed in the outer ring, a considerable cost is required for forming the eccentric groove in the outer ring, and besides it is difficult to completely eliminate a possibility that a slip develops between the stop ring and the outer ring and also between the stop ring and the housing with respect to the relation between the depth of the eccentric groove and the dimension of the inner diameter of a housing hole, since a resilient force of the stop ring is utilized. Therefore, it is difficult to completely solve the problem that creep develops between the outer ring and the housing.
In recent years, with the advanced study of resins, there have been developed resins having excellent mechanical strength. For example, with respect to a one-way clutch used in a drive system of a washing/dewatering basket (rotating vessel) of a washing/dewatering machine, it has been proposed to form a housing of this one-way clutch, using a resin. In the case of using such a resin-molded housing, a certain degree of effect can be expected by the use of the above related technique, but there still remains the problem that the cost for forming the eccentric groove in the outer ring increases considerably.
For fitting the outer ring of the one-way clutch in the hole in the resin-molded housing, it is advantageous to use a method in which the outer ring is integrally connected to the housing by insert molding. In the insert molding method, however, it is substantially impossible to integrally connect the outer ring to the housing by interference fit, and it is expected that there arises a problem that the creep phenomenon (in which the two rotates relative to each other) is liable to develop due for example to the difference in thermal expansion between the two.